1. Field of the Invention
The present invention relates to purification of dental water lines and, more particularly, to ozonating dental water lines in order to provide uncontaminated water at the point of use.
2. Description of Related Art
Tap water in dental offices is similar to tap water in most homes and offices. While this water is generally considered safe to drink, it is never sterile. Most tap water samples contain fewer than 50 cfu of bacteria per milliliter (cfu/ml). However, once the water leaves plumbing lines and enters the long plastic tubing that feeds into dental high-speed handpieces and other dental implements, such as air-water syringes and ultrasonic tooth scalers, the environment changes. Here, the low flow rate, frequent periods of stagnation and large relative surface area of the small bore plastic lines are ideal for microbial contamination.
Water that stagnates in plastic water lines and/or tubing overnight and even during long periods during the day provide bacteria the opportunity to stick to the wall of the lines/tubing. Water, slowly running through the line, provides a constant flow of bacteria that can adhere to the microbes that are already clinging to the wall. A cooperating population of several different species, which depend on each other for survival, continue to multiply and form a matrix that provides nutrients and mutual protection.
This bacterial population is known as biofilm, a microbial mass that is bathed in liquids. Dental plaque is another example of biofilm. Biofilm can also be found in air conditioning units, artificial implants and many types of equipment, including dental anti-siphon and check valves.
The function of the anti-siphon and check valves is to prevent aspiration of patients' fluids into the dental water lines. Unfortunately, these valves often fail to work properly because of biofilm and other factors.
Microbes can get sucked back into the dental water lines as a result of imperfect hygiene or sterilization practices, a transient negative pressure when the drill stops rotating and/or mechanical failure of anti-siphon valves or other mechanisms. Once this happens, pathogens originating from patients' mouths can enter the lines and adhere to existing biofilm and multiply within them.
These microbes, originating both upstream from municipal water supplies and downstream from patients' blood and saliva, are not very numerous initially. Amplification of the microorganisms is nothing less than astounding. Microbial studies of dental water lines reveal bacterial population explosions averaging over 500,000 cfu/ml and often exceeding 1,000,000 cfu/ml.
Thus far, researchers have identified pathogens and opportunists in dental equipment such as Pseudomonas, Legionella, Staphylococci, Streptococci, Nocardia, Serratia, Klebsiella, Moraxella, Bacteroides, Flavobacterium, Escherichia, several species of amoebae known to serve as hosts for Legionella pneumophila and even nematodes (worms).
Various solutions to prevent exposure of dental patients to contaminated water have been proposed. Such proposals include flushing the dental water lines with distilled water or chemicals but little evidence exists that such flushing eliminates the biofilm. Sterilization of dental instruments between patients has little effect in preventing the microbes in the dental water from entering the next patient's mouth. Using new disposable sterile water lines between patients does not solve the problem of biofilm upstream of the replaced lines and the costs are significant. Use of containers having sterile or distilled water is effective only if the water conveying lines are replaced after each patient arid if the water does not become contaminated prior to disposal of used water lines. Use of check valves to prevent backflow is essentially ineffective one hundred percent of the time due to contamination of the valve itself. Use of electrical current in combination with antimicrobial agents is impractical due to unavailability of inexpensive ready-to-use equipment. Distilling the water received from a municipal water source only addresses the water and not the contaminants present in the lines conveying the water to the patient. To date, devices using 0.2 micron filters or the like is reasonably effective to prevent transmission therepast of microbes provided that the filters are replaced at least daily and that the process of such replacement does not permit a colony of microbes to be conveyed to a water line downstream of the filter. It is therefore evident that a significant health hazard exists for patients within a dental office and no viable solution is presently commercially available.